We know how it turned out, but the people there waiting for the test did not know how it would turn out. The bomb might not have worked. Or it might have ignited a fusion reaction in the atmosphere and destroyed the world. Hans Bethe had sat down and done the calculations on that exact scenario and said it would not, but there was always the possibility of missing something. Enrico Fermi was offering bets on it on the day of the test, as a dark joke.
In the end it worked as expected; one of the most successful and horrifying experiments in the history of science.
Of all the photos from the test the one that struck me the most looking through them today was the photograph of the plutonium core being carried into the ranch house for assembly in a little heavy box. It’s a small thing, about the size of a grapefruit, although twice as dense as lead. It looked just like a sphere of any old metal, but it was something profoundly alien, made inside nuclear reactors. And it still is so strange to me that something that small has so much energy locked up inside and that, by imploding the little sphere just right, we can let the demon out.
Trinity is one of the pivotal moments in the history of our species and eighty years on we still don’t know what the eventual consequences of it will be. The bombs are still here waiting for us and they still pose all sorts of terrifying questions for the future that most people prefer not to think about.
When one looks at the history one needs to remember that these were scientists and engineers who behaved as such. My grandfather, for example, was the sort of person who always loved blowing things up. He'd nearly blown up the family home as a kid when given a chemistry set ... and he studied chemistry because he liked blowing things up ... and he wrote a PhD thesis about the shock waves generated by blowing up a really big (conventional) bomb. It all gets dressed up as studying shock waves and so forth, but it's really kids blowing things up. They get caught up in the challenge of it. The consequences, political, moral and otherwise, are not forefront in the thinking of most. None of them are innocent, but some have misgivings or second thoughts. Others are more cynical and ambitious and even sinister. There are Oppenheimers and there are Tellers.
"The “near zero” chances Oppenheimer unnerves Groves with in-movie probably come from Manhattan Project physicist Arthur Compton, who told author Pearl S. Buck in a 1959 interview that they’d calculated the odds at “slightly less than one-in-three-million.” In 1975, Bethe denied that there had ever been a less-than-one-in-three-million chance of setting the atmosphere on fire, but the idea had already lodged itself in the public imagination."
https://www.inverse.com/science/did-oppenheimer-really-worry...
Someone's got to explain to me how this was even remotely plausible.
We've had orders of magnitude more energetic events in earth's history that they would be aware of (dinosaur slaying asteroid for instance). These didn't manage to destroy the earth by turning the atmosphere into a fusion reactor. Surely they were aware of this.
So was the theory that neutrons are somehow special in a non-thermal way for causing fusion (not fission). And specifically that a concentrated neutron burst could somehow set off a chain reaction? And I guess that [edit: solar] neutrons weren't concentrated enough to cause this even at a detectable level?
E. O. Lawrence's 1930 cyclotron could generate protons at roughly a million degrees Celsius. But that's a single proton stream. Good for splitting atoms but not for fusing them. You really don't know what the cross section of a fusion reaction is until you do it. The properties of matter at that temperature are just super weird. If it had turned out that there was, e.g., a carbon-carbon fusion reaction with a lower initiation, that might be enough to "go critical" and kick off more fusions, and propagate around the world. According to estimates, the Chicxulub crater was 1-10,000 degrees C. Not even the same ballpark.
But, and I'm not sure how much of this they knew back then, we do get bombarded by high-energy cosmic rays, so chances are one of these hypothetical N or O reactions should've already randomly occurred at least in isolated events over the last few billion years if possible.
You need to understand what a nuclear chain reaction is. https://en.wikipedia.org/wiki/Nuclear_chain_reaction
> We've had orders of magnitude more energetic events in earth's history
It isn't about energy. There was never an unbounded nuclear chain reaction of anywhere near this magnitude on the planet before Trinity. A large asteroid impact doesn't cause a nuclear chain reaction at all. The moon impact melted the entire crust but didn't cause a nuclear chain reaction.
In fact, the only chain reaction that happened at all before Fermi's experiment in 1942 - that we know of - was in Oklo (now Gabon) about 1.8 billion years ago. We didn't learn about that until 1972, and anyway that was more like a controlled reactor pile and it only happened because there was so much more Uranium 235 so early in the Earth's history.
The event at Trinity was completely different because so many neutrons were released at exactly the same instant. They had good reasons to be very confident in their models and calculations, but they were not 100% sure, and as TFA points out, the blast was several times more powerful than most models predicted.
As with other aspects of Earth's history, what's possibly surprising to younger readers here is just how much of Earth's history and the evolution of the Solar System has been uncovered recently. The far side of the Moon was unseen by humans (save for a few percent through lunar wobble / liberation) until the mid-1960s, and wasn't accurately mapped until 1969 --- a version of that map decorated my own bedroom wall as a child, and the story of that map's creation is amazing in itself, see "Race To The Moon with Richard Furno" <https://web.archive.org/web/20090129220141/https://kelsocart...> and <https://web.archive.org/web/20090130150935/https://kelsocart...>.
Close observations of other planets only began in the 1970s and is still fairly thin, though long-duration missions to Jupiter and Saturn have been impressive, though recent. The Jupiter Juno probe mission is still ongoing, having begun in 2016, and the Saturn Cassini-Huygens mission reached its destination in 2004 and culiminated (with a "grand finale" plunge into Saturn's atmosphere) in 2017.
The age of the Earth itself wasn't established until 1956, and at the time of the Trinity tests was still estimated as between 1.6 to 3.0 billion years (the presently-accepted age is 4.54 +/- 0.05 billion years). Plate tectonics wasn't accepted as the principle theory of terrestrial geology until the late 1960s. I've recently seen that this occurred between Neal Armstrong's flights on the Gemini and Apollo manned space programmes, the latter of course being his famous first footsteps (by man, that we know of) on the Moon.
But yes, as others are quite correctly noting here, there's been a huge advance in human knowledge within the span of living memory on all matter of related questions: nuclear reactions, fission, fusion, age of the Earth, major events within Earth's history, its own formation, the forces driving its evolution, and more. Looking back with the lens of the state of knowledge in 2026 is highly deceptive.
1) It’s easy to think about the past in terms of what we now know, and it involves a real effort to put yourself in the shoes of the people living at the time and to imagine the “fog of war” in what they knew. In 1945 nobody had ever tested a nuclear explosion before and there was still all sorts of uncertainty about it. And as one of the other commenters pointed out, in particular there was a lot of uncertainty about how fusion worked.
2) The center of the Trinity fireball did in fact produce hotter temperatures than had ever existed on Earth before. Temperature and energy being different things.
In some sense the final experimental proof that a nuclear explosion would not set off some unanticipated new chain reaction that would destroy the earth - unlikely, but hard to completely disprove - was Trinity itself. Only after Trinity is it obvious and completely proven how the physics actually worked and obvious that there were no additional reaction pathways that got missed. That is a disturbing thought.
And then of course there are versions making it into a much more dramatic story.
When they were working on the fusion bomb (and Edward Teller was working on fusion full time already during the Manhattan project), it took some years to establish that even the "easy" to fuse deuterium cannot be set of by simply blowing up a fission bomb. The reaction simply did not propagate for any reasonable dimensions of the system. For any other material the energy balance would have been orders of magnitude short of what was required for a propagating fusion burn.
By the conclusion, the joke about the “near zero” physical possibility of the end of the world has transmuted in Oppenheimer’s mind into certainty that Trinity ignited social forces leading to the same doom.
Bethe called it “absolute nonsense”—interview: https://johnhorgan.org/cross-check/oppenheimer-bethe-and-the...
Here's a student paper giving a pretty thorough analysis (AFAICT): http://large.stanford.edu/courses/2015/ph241/chung1/
Here's more discussion of it: https://history.stackexchange.com/questions/52802/where-did-...
And here (drumroll) is the original paper: https://web.archive.org/web/20200331041344/https://fas.org/s...
(I'm not an expert, though, this is a guess)
The implosion design is tricky. You need to arrange and detonate the explosives precisely to compress the core evenly from all sides, otherwise it shoots out the side or otherwise doesn't go bang the way you want it to. Hence the test.
That trickiness can be a good thing. Almost all modern weapons use the implosion design, partly because it's much safer. With a gun-type design, an accident could easily cause the two pieces to contact each other, resulting in an unwanted detonation. With an implosion design, accidentally setting off the explosives is very unlikely to set them off with the correct timing, so you'll probably just lose the core.
The implosion design is also a lot more efficient. Little Boy used 64kg of uranium. Fat Man used just 6.2kg of plutonium and even got a bigger bang out of it.
Whoa. Its hard to imagine you could have enough conventional explosives to compress a dense metal by ~10x (?). You'd need some serious containment to direct that energy inward rather than outward. I suppose I have some reading to do.
> If you’d like to pinpoint the instant when the world entered the nuclear age, 5:29:45 a.m. Mountain War Time on 16 July 1945
So, I went digging because time zones have been a weird fascination for me due to dealing with all their annoyances as an engineer, and found this article from 2019 [0]!
From the article:
> In February 1942, Congress implemented a law instating a national daylight saving time to help conserve fuel and "promote national security and defense," which is why it was nicknamed "war time." The time zones were even known as that: Eastern War Time, Pacific War Time, etc.
[0] https://www.war.gov/News/Feature-Stories/story/Article/17791...
edit: grammar
[1] https://www.firstwebombednewmexico.com/ [2] https://en.wikipedia.org/wiki/Downwinders#Current_status [3] https://en.wikipedia.org/wiki/Radiation_Exposure_Compensatio...
> On July 4, 2025, in a historic and unexpected move, Congress expanded RECA legislation, finally awarding overdue compensation to New Mexico families. Our newly revised film captures this emotional victory.
Were the families (at the very least) compensated to some extent at last?
You can see the few little bits of tower legs, what is left of the trinitite on the ground, and are surrounded by the enormous quiet of the empty desert all around you. It definitely felt like a haunted place. Not in the literal "there are ghosts here" way. Similar feeling to what I had at Dachau. Just very uncomfortable to be there.
In Russia we used blueberries from certain region(they were openly sold on marketplaces) to calibrate amateur spectrometers(like RadiaCode 101).
I highly doubt it. The last human will likely live many years in agony, fighting disease and starvation.
People start dying off, and all of a sudden housing prices go down. There's more parks open. The air feels fresher gradually. It's a gradual decline as human influence tapers off near the end. I think it will be more "The Last of Us" than "Mad Max"
Humans living through an event where many people are dying will not be calm and happy, they will panic. There will be factions of people trying to survive and hold society together no matter the cost, others who don't believe or agree with these methods and actively resist, as well as those who seek to exploit the chaos.
COVID was a relatively minor example of this, not even close to an extinction event - how pleasant was existence during that time?
If not for modern comms, I am convinced that even in a cold war USA vs USSR style aniliation event, there would still be a handful of people on the far corners of the earth who would otherwise take weeks or months to learn anything happened.
To use your COVID example, most of us living well outside the cities and suburbia were very little affected by it. The biggest inconvenience I remember was having to go to Walmart at 6:00 when it opened to get a chance at buying toilet paperl
For me it was mostly terrific. We had increased streams of revenue and were food secure for the first time in a decade. Meetings I dreaded due to crowds were streamed online.
And the roads were blessedly, amazingly, wonderfully travelable.
The housing crisis in 2021 was another matter entirely. Our long term rental was sold and what few listings there were got 400 hundred applications - every day.
2020 was excellent for us. 2021 was a slow moving, panic-strewn nightmare.
I will assume this is true and plug it into our falling birthrates.
People will flock to cities that still have services. Then the cities will have the same population density as before.
Ted Kaczynski had a point...
I wasn't being intentionally pedantic. I was in fact making a point that the reality will be a lot more grim than watching a giant fireball turn into a mushroom-shaped cloud for a few seconds or minutes.
"Always/Never: The Quest for Safety, Control, and Survivability." (part 1) https://www.youtube.com/watch?v=DQEB3LJ5psk
They cover both the technology itself and its history, including the incidents you are reading about. These people are the ones who developed the methodology and the technology for nuclear device safety, or at least a significant chunk of it. I think it has recently become much more mathematically heavy, with zero knowledge proofs and other fancy stuff used to talk to the locks in the devices.
It had no music and actually (if I recall correctly) had no sound at all for what seemed like the longest time.
It really did make the extreme gravity of the event sink in very deeply.
Fully agree with libraryofbabel's comment here of it being "one of the most successful and horrifying experiments in the history of science".
Imagine a cosmic being looking at the Earth through a microscope, and seeing this bubble pop on the surface in mid-20th century. Then another, and another pop. Some of them evaporated hundreds of thousands of human beings, melting and dying in gruesome ways you can't imagine in the worst nightmares of hell. Later these organisms learn to harness this destructive force for more useful and productive purposes, powering their cities and data centers for machine intelligence. And this massive amount of energy is released by breaking up the tiniest particles of matter, the nucleus of an atom, how clever and strange is that. Well, no more strange than the phenomenon of life itself, I suppose.
But likewise, there was only a few decades between the first airplane and the first person on the moon (although rocketry goes back hundreds of years. Actually TIL rocketry is older than Newton's laws of physics)
https://www.astronomy.com/today-in-the-history-of-astronomy/...
Luckily, the Times did issue a correction - almost 50 years later, on July 17, 1969. The day after NASA launched the first mission to the moon.
The survival of the human species relies on its ability to expend energy. Grow food? We need gas to run the tractors.
Travel to your jobs? Gas or electricity.
Travel to another planet? Massive amount of energy.
Ride away on a spacecraft to another solar system? Massive amount of energy.
The amount of energy required to do these things is probably more than the amount of energy required to erase ourselves from existence. And when we have the ability to harness that energy, do we really think we are responsible enough to not do that, accidentally or adversarial-y?
It looked like someone set off a bunch of chemical explosives. That’s not how it looked in real life. Totally bizarre decision. I don’t know if they were trying to avoid effects on purpose of go gritty and retro or something but the “unearthly cosmic horror” feel of the first a-bomb blast is important. It’s what led Oppenheimer to recite “I am become death, destroyer of worlds.”
/hah very articulate of me for this early in the morning
But Nolan intentionally hamstrung himself by eschewing CGI in favor of practical effects. I mean in theory you could do a practical effect of a nuke but that requires detonating a nuke; the west hasn't done that since 1992, the last nuclear detonation was done by North Korea in 2017.
https://www.realcleardefense.com/articles/2026/05/21/why_pre...
I’m in Australia, so it’s only a (relatively) short drive to Woomera.
We should make sure our (the West’s) nuclear deterrent still actually works, and put the fear of God back in to everyone.
And also demonstrate how relatively benign the fallout from a thermonuclear weapon is, ie. relatively little radioactive material is generated from modern nuke.
https://en.wikipedia.org/wiki/British_nuclear_tests_at_Maral...
Every time I see a photo or video of a nuclear explosion, it's simultaneously the most incredible thing I've ever seen and the single worst thing I've ever seen. I can't imagine what it must have been like to witness it first-hand, with no prior expectation of how monstrous a nuclear explosion would be until there it is in front of you in an instant.
https://www.purplewave.com/auction/210310/item/IG9246/US_Arm...
The Little Boy gun-type detonation of enriched Uranium is indeed fairly trivial, and end for its first use at Hiroshima they were confident enough to deploy it without full scale testing.
https://reddit.com/r/interestingasfuck/comments/zl72x5/submi...
And his movie is Trinity and Beyond
See also atomcentral.com
